The invention resides in the mechanical field, and more particularly in the medical engineering field, and relates to a sheath device for inserting a catheter into a patient's body.
Especially in microinvasive or minimally invasive applications in the medical field, functional elements such as stents, milling heads for clearing blood vessels by milling, or cardiac support pumps, are frequently inserted into the interior of a patient's body, specifically into endogenous vessels, and more particularly blood vessels, through an opening by means of catheters. So as to be able to insert such catheters once or several times while minimizing the traumatization of the affected tissue, and also while minimizing the risk of damage to the sensitive medical devices, sheaths are frequently employed, which are permanently or temporarily introduced in a patient's body and which have an inner lumen, which allows a catheter or other functional elements to be guided through. The Seldinger Technique, which will be described in more detail below in connection with FIG. 1, is known for inserting such a sheath into the patient's body.
A corresponding method is known from WO 02/43791 A1, for example.
Once such a sheath is installed, it can be used permanently or repeatedly for inserting and removing a catheter.
A special application lies in the use of such a sheath for compressible blood pumps or other functional elements, which are first compressed, notably radially compressed, so as to allow better introduction into the body, and then inserted in the compressed state through the sheath to the site of use or to the vicinity of the site of use, whereupon they are expanded. For this purpose, corresponding blood pumps are known, which comprise a pump head at the distal end of a hollow catheter, wherein the pump head comprises a rotor having radially expandable delivery blades and a likewise compressible and expandable housing. The corresponding elements are designed so that they expand automatically, for example if they have been previously elastically compressed, or that they are expanded at the start of a rotary operation by the resistance of the liquid to be delivered, such as the blood (this applies in particular to delivery blades of the rotor).
Other effects, such as shape memory effects in what are known as shape memory alloys, such as nitinol, can, for example, also be used for the purpose of a subsequent shape change.
Corresponding compressible blood pumps are known from WO 02/43791 A1 or from EP 2 047 872 A1, and from DE 100 59 714, for example.
To allow better introduction, such blood pumps or other functional element can advantageously be precompressed by means of an aforementioned sheath and can be kept available, for example in a second sheath, for the treatment of a patient before insertion into the first sheath. The second sheath is then designed such that the functional element, notably the pump head, is held in a compressed state in the interior of the sheath (lumen), for example in the same diameter which is also required for insertion into the first sheath, or slightly larger. So as to transfer the pump from the second sheath into the first sheath, the two sheaths are then typically coupled such that they are coupled coaxially relative to each other at the smallest possible distance from each other, so as to axially displace the pump out of the second sheath and into the first sheath.
This procedure is critical because all components, and the catheter, the pump head and the second sheath in particular, are subjected to high mechanical stress. In addition, it is a problem that under surgery conditions this sheath process must generally be carried out manually using few other aids, placing high demands on the simplicity of the process and on the reliability.